1. Field of the Invention
The present invention relates to a process for upgrading a mixture of oligomers of isobutylene or of a mixture of isobutylene and a minor amount of n-butenes and to the composition of the upgraded oligomers and their use as traction fluids.
2. Discussion of the Prior Art
Streams comprising monomers and oligomers of isobutylene or of a mixture of isobutylene and a minor amount of n-butenes are available from a variety of sources. For example, the manufacture of polyisobutylene from streams comprising isobutylene or of a mixture of isobutylene and a minor amount of n-butenes also results in the production of a large volume of a mixture of oligomers of isobutylene and, if present, n-butenes that have a lower molecular weight than the polyisobutylene produced. This mixture is sometimes referred to as light polymer gasoline and typically is made up primarily of unreacted monomers and dimers, trimers and tetramers of isobutylene and, if present, n-butenes. Such mixtures are commonly used as an inexpensive feedstock in, for example, a refinery. It would be highly desirable to convert components of these mixtures to higher oligomers that are suitable for use in other more valuable applications.
Numerous methods have been reported for converting dimers and trimers of butenes to higher oligomers of butenes. For example, each of E. C. Erdolchemie Gmbh, German Patent No. DE 3611842 and E. C. Petrochemical Gmbh, German Patent No. DE 3612443 A1 discloses a process in which diisobutylene is dimerized in the liquid phase in the presence of a sulphonated cation exchange resin catalyst. The resin is pre-dried at 120-200.degree. C., and the diisobutylene is pretreated with a dried inorganic adsorbent. By means of a partial return of the generated reaction product, it is possible to obtain nearly complete conversion of diisobutylene to tetraisobutylene. In one example, the yield for the conversion of diisobutylene to tetraisobutylene was 95%. There was no disclosure that other oligomers besides tetraisobutylene were formed.
Other references disclose processes that differ in significant ways from the process of the present invention but which produce products that are similar in oligomeric distribution but which products differ from the compositions of the present invention. For example, International Patent Application No. PCT/FI92/00199, published as WO 93/02993 on Feb. 18, 1993, discloses a method for the oligomerization of 1-butene in a single step in the presence of a catalytic complex of BF.sub.3 and either water, a C.sub.2 -C.sub.10 monoalcohol or a C.sub.2 -C.sub.8 monocarboxylic acid as the cocatalyst. Several specific examples of the oligomerization afforded high selectivities for the production of tetramers and pentamers, as follows:
Selectivities for the Production C.sub.4 of C.sub.4 Conversion Conversion C.sub.8 C.sub.12 C.sub.16 C.sub.20 C.sub.24 C.sub.28 C.sub.32 + Example 1 77.4% -- 10.5 51.5 28.2 8.0 1.8 -- Example 9 53.5% 0.3 7.6 43.3 36.8 7.1 5.0 --
In addition, Example 15 afforded combined selectivities of 57.0% for dimers, trimers and tetramers and of 43.0% for pentamers, hexamers and heptamers.
International Patent Application No. PCT/FI93/00540, published as WO94/15895 on Jul. 21, 1994, discloses a method for the oligomerization of olefins containing 6 to 20 carbon atoms or n-butenes in the presence of a catalytic complex of BF.sub.3 and either water, a C.sub.2 -C.sub.10 monoalcohol or a C2-C10 monocarboxylic acid as the cocatalyst. Several specific examples of the oligomerization afforded high selectivities for the production of tetramers and pentamers, as follows:
 Selectivities for the Production of C.sub.8 -C.sub.16 C.sub.20 -C.sub.28 C.sub.32+ Example 19 58.3 39.2 2.5 Example 25 59.6 34.5 5.9 Example 54 63.2 35.6 --
The olefin oligomerized was an n-butene mixture in Example 19, and n-butene in Example 25. In addition, Example 9 in International Patent Application No. PCT/F193/00540 was a duplicate of Example 15 in aforesaid International Patent Application No. PCT/FI92/00199.
Japanese Patent No. 57-159724 published on Mar. 27, 1981 and issued on Oct. 1, 1982 discloses a method for the selective conversion of a dimer of isobutylene to a tetramer of isobutylene in the presence of an aluminosilicate, acid gypsum or activated gypsum catalyst that must be roasted prior to use. The patent illustrates that when equimolar amounts of dimers and trimers of isobutylene are present in the feedstock for the reaction, the method was essentially ineffective. When the molar amounts of the dimers to trimers of isobutylene in the feedstock were in a ratio of 9:1, the method was effective.
Thus far, no one has disclosed a method for converting the aforesaid light oligomers of isobutylene and optionally n-butenes to mixtures of higher oligomers thereof, in which mixtures of tetramers, pentamers, hexamers and higher oligomers are the major components and have the overall oligomeric distribution and iosmeric structure of the composition of this invention.
In addition, it would be highly desirable to develop improved traction fluids. Continuously variable transmissions are expected to be the next generation technology in automotive power transmission. Continuously variable transmissions transmit power through a traction drive mechanism. Traction drive power transmissions, which transmit power to a driven part through a traction device mechanism, have attracted attention in the field of automobiles and industrial machinery, and in recent years research and development thereon has progressed. The traction drive mechanism is a power transmitting mechanism using a rolling friction. Unlike conventional drive mechanisms it does not use any gears, which enables a reduction in vibration and noise as well as a smooth speed change in high-speed rotation.
An important goal in the automobile industry is improvement in the fuel economy of automobiles. It has been suggested that if the traction drive is applied to the transmission of automobiles to convert the transmission to a continuous variable-speed transmission the fuel consumption can be reduced compared to conventional transmission systems since the drive can always be in the optimum speed ratio.
Traction fluid is a term used to identify a class of lubricants that give improved performance in traction drive. More particularly, a traction fluid is used in a device, such as a non-stage transmission device for automobiles, in which traction drive transfers force from one rotating rigid body to another through rolling contact. The traction fluid is applied to such a contact portion to efficiently transmit the driving force and to prevent direct contact between the rigid bodies. Namely, such a traction fluid exhibits an increased viscosity upon being pressed by the rigid bodies to efficiently transfer the drive force with minimum slip but shows suitable fluidity immediately upon being released from the contract portion.
One of the important characteristics of traction a fluid is the coefficient of traction. The higher the traction coefficient, the better becomes the transfer of drive force. With a traction fluid with a high traction coefficient, the traction drive device can be made compact. Another desirable property of a traction fluid is its viscosity. Too high a viscosity causes a loss of energy for the stirring of the fluid and is disadvantageous because the fluid fails to exhibit the required characteristics at the start of the operation in which the fluid is still cold. When the viscosity is considerably low, a liquid film fails to be formed between the contact portion of the rolling members at a high temperature, causing seizure.